Next question. The big end oil ways are just 3/32" holes. On their own twin, the 500 cc KG/KH, Ariel issued a service bulletin advising owners to grind a 'teardrop' into these holes to distribute oil into the bearing.

Simon... Before having a crank ground, I always Dremel Grind a shallow cup across the journal to enlarge the oilway width slightly and restore the wider oil film where oil enters the bearing surface. New cranks had a teardrop or similar cutaway machined in production, but successive regrinds narrow the width of the teardrop cup, until it almost disappears, leaving a very sharp edge to cut a nice central groove in your new shells. Grind the shallow cup first, before grinding the crank, have it ground if necessary, then finally polish the edge again to ensure a smooth transition from oilway to journal surface.

I have already posted my thoughts on this in the thread about the drive side conrod oil bleed hole. It is to do with the reduction of surface area with depth of a shallow cone, like why your vintage Martini Glass seems to empty rather quickly.

G'day Simon.I agree 110% with Swarfy.By enlarging the hole it ends up wider (across the journal) than long (circumferential (thank god for spellcheck)). I double (3/16") it's width with a Dremell.Cheers

Get all the planned machining, grinding etc done first. Put the crank in the freezer and wait.....either until you have free and secret access to the domestic oven or it is barbecue time and either way you can warm that flywheel up nice and gently, til the spit dances, creep up on the cold crank and just drop it together.

Get all the planned machining, grinding etc done first. Put the crank in the freezer and wait.....either until you have free and secret access to the domestic oven or it is barbecue time and either way you can warm that flywheel up nice and gently, til the spit dances, creep up on the cold crank and just drop it together.

I am going to the pub, deserve it after brain work on the yokes , stem etc for the featherybed- long story for another day. swarfy creep up on it sounds good but not like my mate who had his triumph crank case heated up and got the outer bearing race in at an angle and he couldn't centre it up-- it was a swine to get out again once everything was hot